add options for static linking and LTO to CMake builds

Author: striezel

.github/workflows/clang.yml

@@ -27,6 +27,17 @@ jobs:
           cd build
           cmake ../
           make -j2
+      - name: Build statically linked with Clang ${{ matrix.version }}
+        run: |
+          export CXX=clang++-${{ matrix.version }}
+          export CC=clang-${{ matrix.version }}
+          cd $GITHUB_WORKSPACE
+          mkdir build-static
+          cd build-static
+          cmake -DENABLE_LTO=ON -DENABLE_STATIC_LINKING=ON ../
+          make -j2
+        # Only run static build on latest version in the matrix.
+        if: matrix.version == 14
       - name: Run tests
         run: |
           cd "$GITHUB_WORKSPACE/build"

.github/workflows/gcc.yml

@@ -27,6 +27,17 @@ jobs:
           cd build
           cmake ../
           make -j2
+      - name: Build statically linked with GNU GCC ${{ matrix.version }}
+        run: |
+          export CXX=g++-${{ matrix.version }}
+          export CC=gcc-${{ matrix.version }}
+          cd $GITHUB_WORKSPACE
+          mkdir build-static
+          cd build-static
+          cmake -DENABLE_LTO=ON -DENABLE_STATIC_LINKING=ON ../
+          make -j2
+        # Only run static build on latest version in the matrix.
+        if: matrix.version == 11
       - name: Run tests
         run: |
           cd "$GITHUB_WORKSPACE/build"

.github/workflows/msys2.yml

@@ -37,3 +37,13 @@ jobs:
           export MSYSTEM=MINGW64
           cd "$GITHUB_WORKSPACE/build"
           ctest -V
+      - name: Build statically linked
+        run: |
+          export MSYSTEM=MINGW64
+          export CXX=g++
+          export CC=gcc
+          cd $GITHUB_WORKSPACE
+          mkdir build-static
+          cd build-static
+          cmake -DENABLE_LTO=ON -DENABLE_STATIC_LINKING=ON ../
+          cmake --build . -j2

CMakeLists.txt

@@ -1,8 +1,38 @@
-# We might support earlier versions, too, but try to use a recent one.
 cmake_minimum_required(VERSION 3.8)
 
 project(sha256)
 
+# If the option ENABLE_LTO is enabled (e. g. via `cmake -DENABLE_LTO=ON`)
+# during the build, then all binaries will use link-time optimization (LTO).
+option(ENABLE_LTO "Enable link-time optimization" OFF)
+# Not all compilers support LTO / IPO, so it has to be checked.
+if (ENABLE_LTO)
+  cmake_policy(SET CMP0069 NEW)
+  include(CheckIPOSupported)
+  check_ipo_supported(RESULT HAS_LTO_SUPPORT OUTPUT LTO_FAIL_REASON
+                      LANGUAGES C CXX)
+  if (NOT HAS_LTO_SUPPORT)
+    message(FATAL "IPO / LTO is not supported: ${LTO_FAIL_REASON}")
+  else()
+    message(STATUS "IPO / LTO is supported. Using it.")
+  endif()
+endif (ENABLE_LTO)
+
+# If ENABLE_STATIC_LINKING is on (e. g. via `cmake -DENABLE_STATIC_LINKING=ON`),
+# then all libraries are linked statically. The option is off by default.
+#
+# Static linking increases the size of the binaries, but those binaries do not
+# need the libraries to be present on the system.
+#
+# WARNING: This option is still experimental and may not work completely.
+option(ENABLE_STATIC_LINKING "Links all libraries statically" OFF)
+if (ENABLE_STATIC_LINKING)
+  set(CMAKE_LINK_SEARCH_START_STATIC 1)
+  set(CMAKE_LINK_SEARCH_END_STATIC 1)
+  set(CMAKE_FIND_LIBRARY_SUFFIXES ".a")
+  set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -static-libgcc -static-libstdc++ -static")
+endif ()
+
 # Recurse into subdirectory for sha256 executable.
 add_subdirectory (sha256)